JPH10216908A - Method for reusing tundish under hot state - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fully discharge steel and slag remaining in a tundish and to prevent the deterioration in quality of a cast slab at the time of casting in the following time by combining the tilting of the tundish after completing continuous casting and the melting and removing with a burner in reusing the tundish for continuous casting under a hot-state. SOLUTION: The remaining steel and slag in the tundish after completing the continuous casting are concentrated to a specific position in the bottom part of the tundish and inert gas is blown into this specific position. By this method, the tundish 1 giving a tapered part in consideration of further dischargability and increase of the inner contents, is used and the tilting discharge is executed and thus, the discharges at two steps of the first step for reducing the remaining materials in the inner part to the min. and the second step for fully discharging the steel remaining steel and slag with the first step by forcedly heating and melting with the oxygen-enriched burner 7, are executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tundish hot reusing method capable of completely removing residues in a tundish when hot reusing the tundish in continuous casting.

[0002]

2. Description of the Related Art In continuous casting, molten steel in a ladle is once poured into a tundish as an intermediate pan, and then continuously cast into a mold from the tundish through a sliding nozzle and a dipping nozzle. In such a tundish, for the purpose of reducing the cost of refractory, etc., after casting several charges, the remaining steel and residue in the tundish are discharged without cooling the tundish and repairing the refractory. In addition, hot reuse in which a tundish is reused by exchanging consumables nozzles or the like is performed.

In this tundish hot reuse,
The most problematic problem is that the residual steel and residue that cannot be completely discharged from the tundish will extremely increase inclusions in the molten steel at the next casting, degrade the slab quality, and deteriorate the powder in the mold. There was also a problem such as connection and causing operational trouble. Then, conventionally, the following methods for discharging the residual steel and the residue in the tundish have been proposed.

(1) Japanese Patent Laid-Open Publication No. 1-107949 (method of repairing and reusing a tundish without refining) Discharged from the outlet provided between
Then, after discharging most, the remaining steel and the residue are dissolved and discharged by the preheating gas burner provided in the tundish lid while being tilted, and the steel remaining in the nozzle is discharged. It is redissolved and discharged by blowing oxygen gas.

After discharge, the preheating gas burner continues to keep heat, the immersion nozzle is replaced with a new one, and the tundish body is reused without repair.

(2) Japanese Patent Application Laid-Open No. 5-177316 (Tundish and method for reusing the same) The melting point of the residual steel and the residue during the period from the end of continuous casting to the stage of dissolving and removing the residual steel and the residue by a burner. Solid additives (soda ash, coke, etc.) are added to cover the remaining steel, etc., and then an oxygen-enriched burner is placed in the tilted tundish to cover the tundish lid. The remaining steel or the like is intensively heated and dissolved and removed through an opening, and is discharged from a discharge port provided between an upper part of the tundish and a lid of the tundish. Further, the side wall of the tundish on the discharge side is inclined toward the discharge port so that the molten residual steel or the like is easily discharged. That is, as shown in FIG. 9, the discharge side wall inclined at an inclination angle β in the tundish height direction is inclined at an inclination angle α in the longitudinal direction of the tundish, and these α and β are set to 15 ° or more. And

[0007]

However, the prior art (1)
In the method of (1), since the tilting discharge of the residue in the tundish and the subsequent heating and melting by the preheating gas burner are not sufficient, the residue in the tundish cannot be completely discharged (residual steel weight 10 kg, residue 20 kg). . In addition, since this residue is considerably oxidized by the preheating gas burner, there is a disadvantage that the quality of the slab at the time of next casting is adversely affected.

In the method of the prior art (2), an additive is added to improve dischargeability, but by increasing fluidity,
There is a problem that the slag line refractory in the tundish is severely melted and the refractory cost is deteriorated. In addition, it has been proposed that the tundish side wall is inclined in the longitudinal direction of the tundish to improve dischargeability.However, the bottom area of the tundish is reduced and the tundish capacity is reduced. It has been confirmed that there is a problem in operation such as worsening the casting speed and lowering the casting speed in order to prevent this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to combine steel and slag remaining in a tundish by a combination of tilting of the tundish and dissolution and removal by a burner. Of the present invention is to provide a hot re-use method for a tundish capable of completely discharging slag and preventing deterioration of cast slab quality when a tundish hot slag is used.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is to remove a steel and a slag remaining in a tundish after continuous casting, and to re-use the tundish by hot reusing the tundish. In the method, the tundish with its internal shape optimized by the taper of the inner wall of the tundish discharge side is tilted after continuous casting and the remaining steel and slag are discharged from the discharge port provided between the upper part of the tundish and the tundish lid. Discharging, and after discharging the steel and the slag, having a step of dissolving the steel and the slag attached to the tundish using an oxygen-enriched burner and re-discharging from the discharge port. I do.

In the tundish, for example, as shown in FIG. 4, a water pool is provided at the bottom of the tundish at a position where the tundish nozzle is attached, and the steel and the slag are placed between the top of the tundish and the tundish lid. A discharge port for discharging is provided corresponding to the hot-water pool portion, and a taper is formed on the discharge-side inner wall of the tundish, the taper being inclined in the longitudinal direction of the tundish and the inclination angle gradually increasing toward the discharge port. Use what you have.

As shown in FIG. 1, for example, the oxygen-enriched burner is mounted on a burner truck installed so as to be able to move forward and backward with respect to the tundish at the tilt position, and burner holes (preheating holes) of the tilted tundish. ), The tip of which can be inserted is used, and an oxygen-enriched burner is automatically attached to the tundish after tilting discharge, so that the inside of the tundish can be strongly heated.

That is, in the present invention, steel and slag remaining in the tundish after the end of continuous casting are removed, and when the tundish is reused, the residue is removed from the tundish at a specific portion at the bottom of the tundish at the end of continuous casting. In addition, at the stage of discharging the residual steel and the residue from the end of casting, the inert gas is blown into the specific area where the residue is present, and its stirring effect and the contact area between the residue and the refractory are minimized. A taper that minimizes residue in the tundish as much as possible, and has no protrusions such as weirs, and has a drainage side wall that takes into account dischargeability and prevention of decrease in internal volume for ease of discharging. To reduce the internal residue to a minimum by using a tundish with the addition of oxygen and an oxygen-enriched burner to remove the steel and slag which still remain. A complete discharge of the two-stage step of discharging more strongly heated and dissolved.

Regarding the taper, since the tundish itself is tilted to about 130 °, a taper in the longitudinal direction of the tundish for improving the drainage efficiency is not required at the lower part of the tundish. Without providing a taper, the tundish bottom area is kept as it is, and the taper in the longitudinal direction of the tundish becomes a strong taper as it becomes the upper part of the tundish, so that the internal capacity of the level actually used during casting is secured. (See FIG. 4).

[0015] In the above-described structure, in the tundish after casting, as shown in Fig. 4 (a), steel and slag tend to remain at the bottom, and the remaining steel and slag concentrate at specific locations. When the inert gas is blown into the space, the internal residue is prevented by the stirring effect of the inert gas. Further, the residue is guided by the taper in the longitudinal direction of the tundish formed on the side wall on the discharge side of the tundish and the residue flows to the discharge port at a stretch, so that the residue can be reduced. In addition, such a taper allows the bottom area of the tundish to be the same as that of a normal tundish, so that a decrease in the internal capacity of the tundish can be prevented.

From the end of casting to the above-mentioned tilt discharge, four to four times are required for the movement to the tilt discharge position and the setup of the tilt discharge work.
Requires 5 minutes time. Therefore, the steel and the slag still remaining in the tundish after the tilting discharge are partially solidified, and the temperature and temperature of the remaining steel are reduced over time. Then, the oxygen-enriched burner is inserted from the inside, and the inside of the tundish is heated at a stretch, whereby the internal residue is completely dissolved and discharged again. At this time, the internal temperature of the tundish is raised to 1850 to 1950 ° C. to completely dissolve the internal residue. Tundish internal temperature 1
At 850 ° C. or lower, it was confirmed that residues often existed and quality was deteriorated. In addition, when the internal temperature of the tundish is 1950 ° C. or higher, melting of the refractory becomes severe, the life of the refractory is shortened, and it is impossible to reduce the cost of the refractory intended. After re-discharge, the tilted tundish is returned to a normal state, the opening of the tundish is sealed to prevent heat radiation, and preparation for the next use is started.

[Test Example of Highly Heated Waste by Oxygen-Enriched Burner] Casting was completed with the remaining steel in the tundish set to 6 tons. Automatic tilting waste was carried out using the trolley of the waste disposal device shown in FIG. The strongly heated waste was carried out using the oxygen-enriched burner shown. When the strongly heated waste was carried out by the oxygen-enriched burner in the above procedure, the results shown in Table 1 were obtained. In addition, as shown in Table 1, four patterns of strong heating waste were carried out. As shown in Table 1, depending on the burner conditions (C gas flow rate, heating time, oxygen enrichment), the internal temperature of the tundish was set to 1850 to
It was found that the temperature was optimally about 1950 ° C., and that the refractory had little erosion.

[0018]

[Table 1]

As described above, in the present invention, an additive for improving fluidity is used in a conventional tundish by optimizing the internal shape of the tundish and using an inert gas. Efficiently discharge the residue in the tundish to minimize the internal residue after tilting discharge, and further re-discharge the tilted tundish by strongly heating using an oxygen-enriched burner Therefore, it is possible to completely remove the residue on the working surface in the tundish, and it is possible to prevent the quality of the slab from being deteriorated in the next casting. In addition, when the discharge property at the time of tilting discharge is poor, the quality of the slab is likely to be deteriorated even by performing strong heating with an oxygen-enriched burner. Since it is extremely good, it is possible to surely prevent the slab quality from being deteriorated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. This is an example applied to a tundish for two strands. 1 to 3 show a strongly heated waste disposal apparatus equipped with an oxygen-enriched burner for implementing the tundish hot reuse method of the present invention. FIG. 4 shows the shape of a tundish used in the present invention, which has been subjected to measures for improving dischargeability and preventing a decrease in internal capacity. 5 to 7,
The example of the waste equipment in the upper part of a continuous casting machine is shown.

In the present invention, the tundish 1 shown in FIG. 4 is used, and as shown in FIG. 5, after the end of continuous casting, the tundish 1 is moved from the casting position A to the discharge position B by the tundish car 2. The tundish 1 is moved to the tilting position C using the waste trolley 4 of the waste discharging device 3, the tundish 1 is tilted at the tilting position C, and the remaining steel and the residue in the tundish are discharged to the collection container 5. I do. Next, after confirming that the outflow of the remaining steel and the residue has been completed, the strongly heated waste discharging apparatus 6 shown in FIG. The residue is subjected to strong heating dissolution by the chemical burner 7.

The tundish 1 is, as shown in FIG.
It comprises a tundish body 10 and a tundish lid 11. At the mounting position of the sliding nozzle / immersion nozzle at the bottom of the tundish body 10, a pool 12 for concentrating the residue after the casting is provided,
The discharge port 1 is provided at the upper part of the side wall 10a on the discharge side which becomes lower when tilting.
3 are provided corresponding to the position of the pool 12. An inert gas G can be blown into the pool 12 from a nozzle hole at the bottom of the tundish. The tundish lid 11 is provided with a total of four preheating holes 14.

On the inner surface of the side wall 10a of the tundish main body 10, tapers 15, 16 inclined in the longitudinal direction of the tundish for improving the removability of the residual steel a and the residual b are provided.
Are formed. In the conventional FIG. 9, the lower part of the tundish body is also tapered, but the tapers 15 and 16 in the longitudinal direction of the tundish are not formed at the lower part of the tundish body 10 to secure the bottom area of the tundish 1. Ensure that the content does not decrease. That is, the taper 15 has the side wall 10a inclined at the inclination angle β in the height direction.
Is formed at the center of the inner inclined surface 10b at an inclination angle θ (for example, 8 °) with a downward slope toward the discharge port 13. Therefore, the taper 15 is inclined with a downward slope from the inner normal ridge line p in the center toward the left and right sides, and the inclination angle with respect to the inclined surface 10b gradually increases from the bottom of the tundish toward the top. The taper 16 is inclined with a downward gradient from the inner normal q of the corner toward the center. In the illustrated example, the number of outlets is two. However, when the number of outlets is one at the center, the taper 15 may be provided on both left and right sides.

As shown in FIG. 5 to FIG.
It has a waste trolley 4 on both sides of the main body, which can travel on a gantry 20 installed so as to straddle the traveling path of the tundish car 2 at the waste position B.
The upper tundish 1 is lifted and traversed, and tilted at the tilt position C. The lifting cylinder 2 is mounted on the waste trolley 4.
An elevating platform 21 which can be moved up and down by the guide rod 23 and the guide rod 23 is attached. Mounted. Also,
The tilting frame 24 is moved by the tilting motor 25
Tilt against.

As shown in FIG. 1, the strong heating and discharging device 6
A total of four oxygen-enriched burners 7 are mounted corresponding to the preheating holes 14 of the tundish lid 11 on a burner truck 32 which can move forward and backward on a truck rail 31 of a support member 30 installed above the recovery container 5. It is configured. Fuel gas (C gas) and air + oxygen are supplied to each oxygen-enriched burner 7 by flexible hoses 33 and 34. The burner truck 32 advances into the tundish 1 which is carried into the tilt position C and tilted by 135 °, for example, and the tip of the oxygen-enriched burner 7 is inserted into the preheating hole 14. Therefore, each oxygen-enriched burner 7 is installed on the burner truck 32 at an upward inclination angle corresponding to the inclination angle of the tundish 1. A heat-insulating disk 35 is provided at the tip of each oxygen-enriched burner 7, and a heat-insulating plate 36 is also provided on the front and lower surfaces of the apparatus main body 31.

In the above configuration, the capacity is 72 tons.
After casting 4 charges with the tundish 1, the casting is finished while leaving 4 tons of molten steel and slag in the tundish, and the tundish car 2
Was moved from the pouring position A to the waste discharging position B. During this time,
Inert gas G was injected from the bottom of the tundish 1 and the molten steel was stirred. At the discharging position B, the tundish 1 is lifted from the tundish car 2 using the discharging trolley 4 of the discharging device 3 and moved to the tilting position C, and the tundish 1 is tilted at the tilting position C by 135 °. , Two outlets 1
From 3, the remaining steel and slag were discharged to a collection container 5.

Next, after confirming that the residue has flowed out from the discharge port 13, the strong heating and discharging device 6 is advanced while the tundish 1 is tilted, so that the four oxygen-enriched burners are moved. 7 was inserted into the preheating hole 14, and the residue was strongly heated and dissolved. The conditions of this burner were as follows: C gas flow rate: 1000 Nm ³ / hr Oxygen enrichment: 60% Heating time: 15 min After discharging the residue from the residue, the four oxygen-enriched burners 7 are removed by retracting the high-heat discharging device 6, the tilt of the tundish 1 is returned to a normal state, and the opening of the tundish 1 is closed. Seal all to prevent heat radiation,
The casting tube and the immersion nozzle on the top of the tundish were replaced to prepare for the next casting, and the tundish was hot reused.

FIG. 8 shows the effect of improving the quality of the slab during hot reuse in the above embodiment of the present invention.

In FIG. 8, the tundish is used once when a tundish that has been repaired every time is used, and the slab quality is good. However, the refractory basic unit deteriorates. The multiple use of the tundish is a conventional example in which the discharge is performed only by the tilting of the tundish, and the refractory basic unit and the like are improved by the multiple use, but the slab quality is deteriorated. On the other hand, according to the method of the present invention, the slab quality is improved at the same level as when the repair tundish is used every time, and the basic unit of refractory is also improved. That is, in the embodiment of the present invention, since the residue in the tundish is completely discharged as compared with the conventional example, it is possible to prevent the deterioration of cast slab quality due to the residue. In addition, it was confirmed that the level of erosion of the refractory was almost no problem.

[0030]

As described above, in the tundish hot reusing method of the present invention, the tundish having an optimized internal shape is tilted after continuous casting, and the remaining steel and slag are removed from the tundish upper portion and the tundish. Discharging the steel and the slag adhering in the tundish using an oxygen-enriched burner after discharging the steel and the slag and discharging the steel and the slag again from the discharge port. Because of the stages, the following excellent effects can be obtained.

(1) In addition to concentrating the residual steel and the residue at a specific portion of the tundish, an inert gas is blown into the tundish to prevent the internal adherence, and to optimize the internal shape of the tundish to reduce the residue. By minimizing the residue from the tilting discharge of the tundish, the residue that has been minimized can be strongly heated using an oxygen-enriched burner while the tundish is tilted. Since it is dissolved and re-discharged, the residue in the tundish can be completely discharged.

(2) Since the residue can be completely removed, it is possible to prevent the deterioration of cast slab quality, which has been a problem at the time of hot reuse in a tundish, and to stabilize the quality. In addition, it is possible to achieve the purpose of reducing the cost of refractories by using the tundish many times while ensuring stable quality.

(3) Since no conventional solid additives are used, the melting of the tundish refractory can be prevented. Further, by optimizing the internal shape of the tundish, it is possible to prevent a decrease in the tundish capacity, and it is possible to solve the problem caused by the decrease in the tundish capacity.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a strongly heated waste disposal apparatus equipped with an oxygen-enriched burner for carrying out the tundish hot reuse method of the present invention, wherein (a) is a state before tilting discharge and (b). ) Indicates the time of strong heating and melting after tilting.

FIG. 2 is a plan view of the strongly heated waste discharging apparatus of FIG.

FIG. 3 is a front view of the strongly heated waste discharging apparatus of FIG. 1;

FIG. 4 is a tundish used in the present invention, wherein (a)
Is a longitudinal sectional view, (b) is a perspective view, (c) is a top view, and (d) is a transverse sectional view.

FIG. 5 is a plan view showing waste equipment at an upper part of the continuous casting machine.

FIG. 6 is a front view of the waste equipment of FIG. 5;

FIG. 7 is a side view of the waste equipment of FIG. 5;

FIG. 8 is a graph showing a slab quality index according to the present invention.

FIG. 9 is a sectional view showing a conventional tundish.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tundish 2 ... Tundish car 3 ... Drainage device 4 ... Drainage trolley 5 ... Recovery container 6 ... Strongly heated drainage device 7 ... Oxygen-enriched burner 10 ... Tundish main body 11 ... Tundish lid 12 ... Hot water pool Part 13: Discharge port 14: Preheating hole 15: Taper 16: Taper 20: Stand 21 ... Lifting table 22 ... Lifting cylinder 23 ... Guide rod 24 ... Tilt frame 25 ... Tilt motor 30 ... Support member 31 ... Truck rail 32 ... Burner truck 33 ... Flexible hose (C gas) 34 ... Flexible hose (air + oxygen) 35 ... Heat-proof disk 36 ... Heat-proof plate

Claims (3)

[Claims] 1. A tundish hot reuse method for removing steel and slag remaining in a tundish after the end of continuous casting, and reusing the tundish. Tilting the tundish after continuous casting to discharge the remaining steel and slag from the outlet provided between the upper part of the tundish and the tundish lid, and oxygen-enriching after discharging the steel and slag A method for hot-reusing a tundish, comprising the step of dissolving steel and slag adhering to the inside of the tundish using a burner and re-discharging it from the outlet. 2. The tundish hot reusing method according to claim 1, wherein the tundish is provided with a water pool at a position on a bottom portion of the tundish where a tundish nozzle is attached, and a tundish upper portion and a tundish. A discharge port for discharging the steel and the slag is provided between the lids in correspondence with the pool, and the discharge side inner wall of the tundish is inclined in the longitudinal direction of the tundish, and the inclination angle is set to the discharge port. A tundish hot reuse method, characterized in that a taper that gradually increases in size is formed. 3. The tundish hot reuse method according to claim 1 or 2, wherein the oxygen-enriched burner is mounted on a burner bogie provided so as to be able to move forward and backward with respect to the tundish at the tilt position. A hot tip reusing method, characterized in that the tip is inserted into a tilted tundish burner hole.